One such fuel distribution system as disclosed by Walter et al in U.S. Ser. No. 217,297 filed Dec. 17, 1980, illustrates a fuel system including a plurality of diesel fuel injectors having a metering chamber. Each diesel fuel injector further includes an intensifier piston having a capillary restrictor that is inserted within a fuel passage within the piston. The upper surface of each piston is connected to a pump via an injection or feed line while each metering chamber is connected to, via a drain line, a common manifold and to a secondary source of fuel such as a low pressure fuel accumulator. The pump is of the type that can selectively pressurize the fuel lines to periodically force the intensifier piston downward thereby initiating fuel injection. Thereafter, the pump relieves the pressure within these lines to permit the intensifier piston to move upward and to let fuel flow from the secondary fuel source into the metering chamber thereby premetering or charging the fuel injector with a predetermined quantity of fuel prior to the next injection cycle or event.
Fuel systems such as that disclosed by Walter et al generate pressure waves due to the rapid cycling of hydraulic events. If proper care is not taken to control the line dynamics, the system may operate inefficiently and reduced control of the system will result. In addition, because of the common connection of the fuel injectors at the manifold, these systems are subject to cross coupling of pressure waves between the respective drain lines.
The invention is illustrated in a fuel delivery system having metering and injection modes of operation, for injecting fuel into the combustion chambers of a diesel engine, comprising a fuel reservoir and pump means for extracting fuel from the fuel reservoir and for selectively applying pressurized fuel to one fuel injector of a plurality of fuel injectors and for selectively depressurizing a particular one of the plurality of fuel injectors wherein the pressurizing and depressurizing are performed in correspondence with the combustion process within the engine. The system further includes a plurality of fuel injectors wherein each fuel injector is adapted to inject fuel within the engine, and has a metering chamber for accepting a determinable quantity of fuel prior to delivery of the fuel to the respective combustion chambers of the engine in correspondence with the combustion process therein and a plurality of injection lines interconnecting each of the fuel injectors with the pump means, wherein each injection line is characterized in having a determinable impedance. The system additionally includes pressure source means connected to the fuel reservoir for establishing a pressure level of fuel intermediate the pressurizing and depressurizing pressure levels applied to the plurality of fuel injectors; and drain line means, for carrying fuel between each of the fuel injectors and the pressure source means including a fuel carrying conduit, one associated with each of the fuel injectors, having an impedance which bears a preselected relationship to the impedance of a corresponding one of the feedlines and, having located therein flow restricting means for restricting the flow therethrough, wherein the flow restricting means has an impedance level to flow which bears a preselected relationship to the impedance of a corresponding one of the drain lines. In addition, the drain line means further includes valve means, connected in parallel across the flow restricting means, for diverting fuel flow from the flow restricting means during intervals of time when fuel is flowing from said pressure source means towards a particular one of the fuel injectors.